1. Field of the Invention
The present invention relates to an image generating device, and particularly to an image generating device for generating a fluorescence image from fluorescence emitted by the subject due to excitation light cast on the subject.
2. Description of the Related Art
In recent years, diagnostic techniques are known in which self-fluorescence emitted from living body or fluorescence emitted from chemicals injected to the living body is detected and represented as a two-dimensional image. Such a fluorescence image assists in the diagnosis of degeneration of the living body tissue or the state of disease (e.g., the kind of disease, infiltrating area) such as cancer and so forth.
The living body tissue which receives excitation light emits fluorescence with a longer wavelength than that of the excitation light. Examples of fluorescent materials contained in the living body include: NADH (nicotinamide adenine dinucleotide); FMN (flavin mononucleotide); pyridine nucleotide; and so forth. Recently, the relation between such living-body-originated-materials and disease has come to be better understood. On the other hand, HpD (hematoporphyrin), Photofrin, ALA (δ-amino levulinic acid), are readily accumulated in cancer tissue. This allows diagnosis of disease tissue by observing the fluorescence emitted from the aforementioned material injected into the living body.
For example, a technique is disclosed in Japanese Unexamined Patent Application Publication No. 8-252218, in which exciting laser light is output from the distal end of a light guide of an endoscope for fluorescence observation.